Exemplary embodiments of the present invention relate to a composite brake disk for a motor vehicle, comprising a brake disk chamber and a brake ring.
In current one-piece cast brake discs both the brake ring and the brake disk chamber are manufactured from a cast material. A disadvantage of this one-piece type of construction is the high, unsprung weight. In order to reduce the weight, composite brake disks increasingly being used, which have a chamber made from an aluminium material and a cast iron brake ring. Although the weight of such a composite disk brake can be reduced by using this material pairing, the different thermal expansion coefficients of the materials of the brake disk chamber and of the brake ring leads to problems. Therefore, composite brake disks are also increasingly available on the market in which the brake disk chambers are fabricated from steel or another material containing iron. A steel sheet is typically used for this purpose, in order to reduce the weight of the brake disk.
German Patent Document DE 10 2009 012 216 A1 discloses such a composite brake disk with a break disk chamber constructed from steel sheet and a brake ring. The brake ring comprises two parts, namely two friction rings, which are separated from each other and connected to each other via studs. Thus, channels are formed between the two friction rings due to the separation between the two friction rings, through which the ambient air flows, and is thus able to convey heat away. One of the friction rings is equipped with an internal tooth profile, into which the tooth profile of the brake disc chamber is inserted. To provide axial security and mounting support, clips and support elements are formed on the brake disk chamber. By means of the clips and support elements a floating mounting of the friction ring on the brake disk chamber is achieved, so that a certain amount of play remains in the axial direction and also in the radial direction. Accordingly, the different amounts of thermal expansion of the friction ring and of the brake disk chamber can be adjusted.
Exemplary embodiments of the present invention are directed to an improved a composite brake disk, which is characterized by a simple, component-based positioning of the mating brake disk chamber and brake ring components.
In accordance with exemplary embodiments of the present invention, a brake disk chamber is equipped before the jointing process, at least at its open end, with a brake disk chamber tooth profile and to form at least one brake ring in such a way that it is equipped before the jointing process with an internal brake ring tooth face, whereby the brake disk chamber tooth faces of the brake disk chamber teeth, as well as the brake ring tooth faces of the brake ring tooth profile have different fits in the jointing area.
Preferably the brake disk chamber tooth profile has a brake disk chamber tooth face of circular arc form, whereas the brake ring tooth profile has tooth faces in the form of an involute.
If both tooth profiles are dimensioned oversize in respect of one another, the two components can be joined by means of the over-sizing, whereby a stressed condition exists between the individual joined components, which facilitates a fixing of the brake disk chamber and brake ring. Through such a development of the tooth faces of brake ring and brake disk chamber a simple, component-centered positioning of the joint component partners is obtained by means of the principle of tooth face centering, whereby the brake ring tooth faces and/or the brake disk chamber tooth faces can be subjected to elastic-plastic deformation during the jointing process. The named teething format should not be confused with a spline/involute spline, as described for example in DIN 5480, since on at least one tooth profile an elastic-plastic deformation occurs. Thus, the method involved here is principally a “face-centered” construction with the aim of achieving a defined state of stress, even under different torque loadings and different amounts of engagement (“bite”) between brake disk chamber and brake ring.
In an advantageous further aspect of the present invention a gap is arranged between the tips of the teeth and the roots of the teeth of the tooth profile at all operating temperature ranges, so that the tips of the teeth and the roots of the teeth have no percentage contact area and thus the torque is principally transmitted via the faces of the teeth, whereby the basic character of a (tooth) face centering concept is provided.
Furthermore, the brake disk chamber in the unequipped state has a basically conical form, whereby the brake disc chamber has a gradually increasing reference teething diameter towards its open end. Thus, the increasing elasticity can be compensated and also in the axial direction a uniform percentage contact area can be obtained.
Furthermore, it is advantageous if the circular arc of the chamber-side tooth faces are laid out relative to the tooth face form in the brake ring such that an as wide as possible contact pattern is achieved via the tooth faces, so that the surface pressure is kept as low as possible and is distributed as evenly as possible. Here, the term contact pattern is refers to the contact zone of the tooth faces with each other in the assembled condition.
During the joining process at least the brake disk chamber experiences both elastic and elastic-plastic deformation in the region of the joint. Accordingly, a greater and more efficient utilization of material is achieved than in the case of a conventional elastic layout. It can be shown that the elastic-plastic deformation is due to the higher pressing-in forces on the initial joining in comparison with a repeated, second joining process.
Further important features and advantages of the invention result from the claims, the drawings, and the associated descriptions based on the figures.
It is clear, that the above named and the following features, yet to be explained, can be used not only in the respective given combination, but also in other combinations or in solitary use, outside the framework of the present invention.